Ukrainian Daria Snigur’s first-ever win on the WTA Tour was a huge one. And the victory wasn’t just for her.

Snigur’s 6-2, 0-6, 6-4 U.S. Open first-round win over Simona Halep — an upset that had the qualifier in tears and the Louis Armstrong Stadium crowd on its collective feet in a standing ovation — was also for her war-torn homeland.

“It’s very good because I won this match,” Snigur said. “I tried to play for Ukraine, for Ukrainian people because I want to support Ukraine. I want to live in the country after war is finished.”

The ongoing months-long war with Russia essentially touched off with the five-week Battle of Kyiv — Snigur’s hometown. Two million people were estimated to have been evacuated from the capital city, with Snigur having actually temporarily relocated to Poland. Temporarily because she has every intention of going back.

In Monday’s first-round match, Snigur, still just 20, showed steely nerves that belied her tender youth. That is, until she polished off the victory over a two-time Grand Slam champion, when she dropped the racket and put her face in her hands and burst into tears. And unlike so many that have been shed in Ukraine of late, these tears were the good kind.

In her second appearance in Louis Armstrong Stadium, the crowd roared its approval, and Snigur waved back. Then she headed to center court and capped her hands in a heart over her pin with Ukraine’s blue and yellow colors.

“I [made the heart] because Ukraine is always in my heart,” Snigur told The Post.

Her first appearance on Armstrong had been at last week’s Tennis Plays for Peace exhibition, ironically to raise money to aid Ukraine. Snigur was determined to use Monday’s victory over the seventh-seeded Halep to help raise awareness.

“When I play tennis, I can ask for people [to listen]. I can talk what’s going on in Ukraine, what happened, because I think people from Europe think the war is finished. It’s not, the war it’s not finished,” Snigur told The Post. “And the Ukrainian people must tell about that, we must support Ukraine. We must tell other people to support Ukraine. It’s very important for us now.”

Halep came in having won 19 of her last 22 matches to vault back into the top 10. But the 30-year-old has struggled in Flushing Meadows in the past, and she suffered her fourth first-round ouster.

When Halep cruised through the second set — committing just two unforced errors to her young foe’s 13 — the veteran appeared ready to seize command in the third.

But those appearances were deceiving. Snigur settled down in the final set, while Halep committed 17 unforced errors herself.

Snigur ran out to a 5-1 lead, and Halep held, broke with a forehand and held again with an ace to claw within 5-4. But she got no closer, Snigur digging deep and winning it with a backhand.

“I was nervous when I had two match points 40-15 and Simona served. And when I lost the game 5-4 I thought maybe I lost. But I tried to fight every ball,” Snigur said. “I lost my concentration sometimes … [but] I saw my father. My father told me, ‘Everything is OK, you must play, you must to fight.’ And so I did.

“It’s very difficult now because I don’t have a base. I’m living in Warsaw, my coach [Larisa Neiland] is living in USA. … Before the war I have plans to play my main draw, to stay in top 100. But during the war plans changed because was based in Kyiv, I live in Kyiv before the war. So after the war my plans changed.”

Relocating to Warsaw; traveling to meet her coach in Riga, Latvia; fighting through qualifiers when she expected a better ranking. And even the uneasy reality of running into Russian players on tour. Snigur — who faces Rebecca Marino in the second round — has seen her plans changed. And dealt with them every time.